The present invention relates to a process and apparatus for spinning a multi-filament yarn, of the general type disclosed in U.S. Pat. No. 4,529,368.
The process of the present invention is distinguished by the fact that, after emerging from the spinneret, the filaments are not subjected directly to cross-flow blowing of cooling air. Rather, the filaments first pass through a first cooling zone with a view to stabilizing the cross-section of the yarn. By this construction, a high degree of uniformity of the filaments is achieved.
However, in the course of further cooling in a second cooling zone, at a preset draw-off speed of 3,000 m/min for example, the chains of molecules are frozen with a pre-orientation. The pre-orientated yarn (POY) produced in this way displays a reduced elongation at break and hence reduced stretchability in the subsequent treatment process.
EP 0 334 604 discloses a process in which, after emerging from the spinneret, the filaments directly enter a blowing stage. In this connection the filaments are cooled with tempered air, whereby a weaker cooling effect is sought in the upper region than in the lower region.
A process is also described in EP 0 726 338 and corresponding U.S. Pat. No. 5,661,880 in which the filaments are additionally warmed immediately upon emerging from the nozzle plate of the spinneret.
In both processes the filaments are blown directly with a current of air with a view to cooling, so that irregularities arise, particularly in the case of thin filaments.
It is accordingly an object of the present invention to provide an improved process of the type described above, as well as an apparatus for the application of the process in such a way that it is possible to produce a yarn having a high degree of uniformity and a high stretching capacity--i.e., a high elongation at break.